In the 3rd Generation Partnership Project (3GPP) that standardizes recent mobile communication systems, the specifications of an Evolved Packet System (EPS) described in NPL 1, which realizes an all-IP network, has progressed. In the 3GPP, an access system connected to the EPS has also been examined in the case of a wireless LAN in addition to LTE.
The 3GPP has examined a proximity-based service (ProSe) described in NPL 2 in the specifications of the EPS. ProSe seek the realization of a service that provides a function (direct communication) of detecting a proximity communication terminal between user equipments (UEs) which are communication terminals or a function of establishing direct communication without using a core network or a base station between the UEs.
In ProSe, since communication is performed without using the core network to which the base station or the access network is connected, it is possible to avoid the concentration in the access network or the core network (congestion avoidance), and it is possible to expect an offloading effect.
In ProSe, a service that searches for and detects communication target UE of the direct communication is required to establish a direct communication path. In ProSe, two methods have been examined as the detection method. The first method is a method (hereinafter, direct discovery) in which the UE directly detects the communication target UE. The second method is a method (hereinafter, EPS discovery) in which the UE detects the communication target UE via the access network or the core network. However, a ProSe service is provided by a mobile communication provider, and needs to be approved by the mobile communication provider for commercial use.
In ProSe, the use of two methods as the direct communication path between the UEs has been examined. The first method is a method of using a LTE access technology. The second method is a method of using, a wireless LAN (WLAN) access technology.
In ProSe, non-public safety and public safety are defined. In the non-public safety, a commercial service provided by the mobile communication provider is assumed, and can be used only in a case where the UE is served by a LTE base station. Meanwhile, in the public safety, the use by a wireless disaster-prevention system is assumed, and can be used both in a case where the UE is served by the LTE base station and a case where the UE is not served by the LTE base station (eNB).